Symptoms of Hypothyroidism in Dogs: Key Signs to Recognize

The thyroid glands, positioned on each side of your dog's neck, are crucial for producing hormones that regulate metabolism, growth, heart rate, and numerous other bodily functions. When these glands malfunction, it can lead to significant health issues for your dog. Understanding how thyroid problems present in dogs and how they are managed helps owners seek timely veterinary attention and support their dog's wellbeing through treatment.

Hypothyroidism, the underproduction of thyroid hormones, is the most common thyroid disorder in dogs. It most frequently affects middle-aged to older dogs and is particularly prevalent in certain breeds including Golden Retrievers, Doberman Pinschers, Irish Setters, and Cocker Spaniels. The most common cause is immune-mediated destruction of thyroid tissue (lymphocytic thyroiditis) or idiopathic thyroid atrophy. Clinical signs are varied and develop gradually, including weight gain without increased appetite, lethargy, cold intolerance, mental dullness, and skin and coat changes such as hair loss, dry skin, and a dull coat. Skin thickening producing a "tragic face" expression is a classic but less common presentation.

Hyperthyroidism, the overproduction of thyroid hormone, is exceedingly rare in dogs and, unlike in cats, is almost never caused by benign thyroid adenomas. When it does occur in dogs, it is most commonly associated with malignant thyroid carcinoma, which presents as a palpable mass in the neck alongside signs of elevated metabolism including weight loss despite increased appetite, increased thirst and urination, hyperactivity, and cardiac abnormalities. Treatment for thyroid carcinoma involves surgery, radioiodine therapy, or radiation depending on the extent of disease. Both thyroid conditions require veterinary diagnosis and management, and thyroid screening through blood testing is increasingly recommended as part of routine health monitoring in predisposed breeds.